Rubbing pad for polishing machines



Jan. 15, 1946. s. A. CRQSBY 2,393,089

RUBBING PAD FOR POLISHING MACHINES Filed Sept. l5, 1944 Patented Jan.15, 1946 of Illinois RUBBING PAD FOR PQLISHING MACHINES Stephen A.Crosby, Chicago,lll.,

Sterling Tool Products Company, a

assignor to corporation Application September 13, 1944, ySerial N o.553,833

4 Claims.

This invention relates to rubbing pads, and more particularly to animproved rubbing pad which may be used on small power driven sanders for4polishing machines. p

'I'he primary object of the invention is to provide an improvedtensioning and gripping mechanism for holding a strip of abrasivematerial on the device.

The present invention is an improvement on the tensioning and grippingmechanism shown in my application Serial No. 504,855, iled October 4,1943.

'I'he invention is illustrated in a preferred embodiment in theaccompanying drawing in which- Figure 1 is a top plan view of a rubbingpad embodying the invention; Fig. 2, a side elevational view of thesame; Fig. 3, a vertical sectional view taken as indicated at line 3-3of Fig. 1; and Fig. 4, a transverse vertical sectional view taken aslndicated at line l. t of Fig. 1.

In the embodiment illustrated, a thin steel backing plate 5 is providedwith upwardly struck dome-like detents 6, positioned to ilt intovsockets which may .be provided on the driving head of a machine, notshown. The backing plate has a pair of keepers I to hold a slidablelatching bar 8, on which exible fingers 9 are mounted. The backing platealso has upwardly extending ribs l0, so that when the latching bar isdrawn rearwardly by its handle Il, the iingers will be exed upwardly andheld in a position from which they may be readily moved into grippingengagement with suitable nibs provided on the driving head, not shown.

The backing plate may be provided with a detent I2 to engage a socket I3in the latching bar 8, when it is in latching position, to preventaccidental disengagement.

A suitable felt -pad I4 may be cemented to the bottom face of thebacking plate E. In order to properly tension a strip of fabric orabrasive such as sand paper around the pad, a special gripping andtensioning mechanism is provided at each end of the backing plate. Itwill be understood that it is only necessary to'have a fastener deviceat one end, if a suitable tensioning and gripping device is provided atthe other. However, it is preferredj to use duplicate mechanism at eachend, so that either may be used as a gripping device and the other asthe tensioning device.

A pair of inverted U-shaped spring keepers I5 are riveted to the backingplate at each' end, as indicated at I8. This cantilever support providesopen Jaws into which the ends of the strip may ilrmly in position.

be inserted. A tubular oval-shaped metal tumbler member I'I is conned bysaid keepers and held against axial movement at each end by guidemembers I8. These members may be formed integrally with the backingplate 5, and are in the form o! upwardly extending ears provided withL-shaped guide slots I9 to permit a screw driver or suitable key,indicated by dotted lines, to be inserted into the ends of the tumblermember I'I.

The backing plate is provided with upwardly extending stops 2u, to limitthe rearward oscillation of the bottom portion of the tumbler. The loopportions of the spring keepers i5 are slightly larger in their topportion than in the mouth adjacent to the backing plate. Accordingly,when the left tumbler member is rotated clockwise from the positionsshown in Figs. 2 and 3, it turns up completely out of contact with theabrasive strip 2l. This leaves an open space, and facilitates insertionor removal of the end of the strip. After the strip has been inserted,the tumbler is turned so that it will engage the strip, press it againstthe backing plate, and pull it towards the center of the backing plateuntil the tumbler strikes the stops 20. During this movement, the upperedge of the tumbler swings across the slot and snaps into the positionshown in Fig. 2, holding the strip An important feature of the presentimprovement is the provision of the L-shaped slots I 8 in the guidemembers I8. These slots limit the oscillation of the key` between thetumbler gripping and a non-gripping position with respect to the stops.As the oscillation of the key is so limited, there is no danger ofcarelessly turning the top of the tumbler against the stops 20 anddamaging the spring keepers I5.

While the rubbing pad illustrated is intended primarily for use on apower driven rubbing machine, it will be understood that the improvedgripping and tensioning mechanism can be used on hand operated rubbingpads, or other devices where a tensioning and gripping mechanism isneeded.

The foregoing detailed description is given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom, for some modilcations will be obvious to those skilled in theart.

I claim:

1. A rubbing pad for a, polishing machine, comprising: a backing plateprovided with means for securing it to a polishing machine; means forsecuring one end of a strip of abrasive material to one end of saidplate and tensioning means at the other end oi said plate for grippingand tensioning said strip about one face of the backing plate includinga flattened hollow tumbler ymember adapted'to engage the striprrictionally to press it against said backing plate, a spring memberhousing said tumbler and adapted to urge the tumbler, against the strip,and an angularly slotted xed guide member near the end of. the tumbler,the slot in said guide member being shaped to permit insertion of a keyinto said tumbler and limit oscillation of the key between a stripgripping and a non-gripping position'.

2. A device as specified in claim 1, in which a guide member is providednear each end of the tumbler member, said guide members serving asabutments to prevent axial movement of said tumbler.

3. A device as specied in claim 1, in which the basking plate is made ofmetal and an integrally formed guide member is provided at each end ofthe tumbler member and are in the form of upwardly extending ears.

4. A rubbing pad for holding a strip of abrasive material, comprising: abacking plate; means for fastening said strip near one end of saidbacking plate; and key-operable tensioning means at the other end ofsaid plate for gripping and tensioning the strip about one face of thebacking plate. said tensioning means having an oval shapedhollow'tumbler member adapted to be turned on edge to engage theabrasiveVv strip irictionally and press it against the backing plate. aspring member for yieldingly urging said tumbler to# wards the plate,and angularly slotted guide members fixed to said plate at each end ofthe tumbler, the slots in said guide member being substantially L-shapedto permit insertion of a key into said hollow tumbler and limit theoscillation by the key between a strip gripping and a non-grippingpositie STEPHEN A. CROSBY.

